The present disclosure relates to a delivery device, including an introducer sheath for deploying, for example, a prosthesis within a body lumen or guiding interventional devices into a body lumen. It also relates to delivery device having an introducer sheath with an adjustable diameter and a mechanism for varying the diameter of the introducer sheath.
Numerous procedures have been developed that involve the percutaneous insertion of a medical device into a body lumen, such as a blood vessel or duct, of a patient's body. Such a device may be introduced into the lumen by a variety of known techniques. For example, a wire guide may be introduced into a blood vessel using the Seldinger technique. This technique involves creating a surgical opening in the vessel with a needle and inserting a wire guide into the vessel through a bore of the needle. The needle can be withdrawn, leaving the wire guide in place. A delivery device is then inserted over the wire guide and into the vessel. The delivery device may be used in conventional fashion to insert into the blood vessel a variety of medical devices, such as catheters, cardiac leads, balloons, stents, stent grafts, and the like.
For example, the delivery device may be used to deliver and deploy an expandable prosthesis, such as a stent graft, at a lesion site to treat a damaged or diseased body lumen such as a bile duct or a blood vessel. A stent graft is usually formed from a tubular body of a biocompatible graft material with one or more stents mounted into or onto the tubular body to provide support therefor. The stents may be balloon expandable stents and/or self-expanding stents. The deployment of the prosthesis into the lumen of a patient from a remote location by the use of an introducer delivery and deployment device is described in, e.g., U.S. Pat. No. 7,435,253 to Hartley entitled “A Prosthesis and a Method and Means of Deploying a Prosthesis,” which is incorporated herein by reference in its entirety.
The delivery device is configured to retain the prosthesis in a delivery configuration during delivery to the lesion site. The catheter typically includes an inner cannula spaced from an outer sheath to define a prosthesis retaining region for receiving the prosthesis. The prosthesis is loaded onto an inner cannula along a prosthesis retaining region, with an outer sheath retaining the prosthesis in the delivery configuration. After the delivery device is delivered to the lesion site, the prosthesis may be deployed, for example, with retraction of the outer sheath relative to the inner cannula away from the prosthesis to allow for expansion thereof. Accurate placement of an appropriately sized prosthesis should sufficiently cover the target lesion site for treatment and the ends of the prosthesis should be engaged with healthy tissue of the body lumen.
It would be desirable to load the appropriately sized prosthesis into an delivery device that is as small as possible. Besides the size of the prosthesis being a factor in the size selection of a delivery device, the shape and size of the body lumen can also be important. Thus, introducing a delivery device that is relatively smaller than the body lumen can avoid potential blockage of fluid or blood flow within the lumen, which can adversely affect the lumen and other parts of the body. Furthermore, the body lumen can be tortuous, thus making relatively smaller delivery devices easier to pass through the tortuous portions.
However, relatively smaller delivery devices can be problematic. For instance, substantial shear forces can be created between the prosthesis and the outer sheath when loading and/or deploying the prosthesis. Such substantial shear forces consequently will require higher pushing or retraction forces when attempting to move the outer sheath relative to the prosthesis during loading and/or deploying. The primary cause of the substantial shear forces is due to overpacking of the prosthesis within the annular space between the outer sheath and the inner cannula. For instance, substantially high overpacking can result when the prosthesis occupies greater than 70% of the annular space. Thus, with the desire to deploy a prosthesis as large as possible with an outer sheath as small as possible, such prosthesis can overfill the annular space. Such overfilling provides greater surface area contact between the prosthesis and the outer sheath and less radially inward movement from the prosthesis. In addition, frictional interference with the outer sheath can be greater than the columnar strength of the prosthesis, which can allow for deformation of the prosthesis in the longitudinal direction, thereby collapsing the prosthesis in an accordion-like fashion. Moreover, rigid portions of the prosthesis, such as the stents and/or barbs, may scrape the inner surface of the outer sheath. Scraping can form debris and thus increase the risk of introducing potential emboli into the body. Scraping can also compromise the retaining strength and weaken the outer sheath, which can allow the outer sheath to bulge undesirably to a larger delivery profile.
Thus, there remains a need to facilitate loading and/or deployment of a prosthesis within a delivery device, and in particular, to reduce the shear forces caused between a prosthesis and an introducer sheath. Further, there remains a need for an introducer sheath that can be radially movable between an expandable configuration, e.g., for reduction of shear forces, and a contracted configuration, e.g., for as small as possible delivery profile, multiple times during loading and deployment of the prosthesis and subsequent to deployment.